# Customizing Webpack Config

For most apps, the default configuration of webpack is sufficient, but sometimes you need to tweak a setting in your
webpack config. This guide explains how to make a small change without taking on the maintenance burden of the entire
webpack config.

{% callout type="note" title="Angular" %}
For Angular developers, use an executor like [`ngx-build-plus`](https://github.com/manfredsteyer/ngx-build-plus).
{% /callout %}

In your `project.json` configuration for the `@nrwl/web:webpack` or `@nrwl/node:webpack` executor, set
the [`webpackConfig`](/packages/web/executors/webpack) option to point to your custom webpack config file.
i.e. `apps/my-app/custom-webpack.config.js`

The custom webpack file contains a function that takes as input the existing webpack config and then returns a modified
config object. `context` includes all the options specified for the executor.

`apps/my-app/custom-webpack.config.js`:

```typescript
// Helper for combining webpack config objects
const { merge } = require('webpack-merge');

module.exports = (config, context) => {
  return merge(config, {
    // overwrite values here
  });
};
```

Also supports async functions

```typescript
// Utility function for sleeping
const sleep = (n) => new Promise((resolve) => setTimeout(resolve, n));

module.exports = async (config, context) => {
  await sleep(10);
  return merge(config, {
    // overwrite values here
  });
};
```

## Add a Loader

To add the `css-loader` to your config, install it and add the rule.

```bash
npm install -save-dev css-loader
```

```typescript
const { merge } = require('webpack-merge');

module.exports = (config, context) => {
  return merge(config, {
    module: {
      rules: [
        {
          test: /\.css$/i,
          use: ['style-loader', 'css-loader'],
        },
      ],
    },
  });
};
```

## Module Federation

If you use the [Module Federation](/recipes/module-federation/faster-builds) support from `@nrwl/angular` or `@nrwl/react` then
you can customize your webpack configuration as follows.

```typescript
const { merge } = require('webpack-merge');
const withModuleFederation = require('@nrwl/react/module-federation');
// or `const withModuleFederation = require('@nrwl/angular/module-federation');`

module.exports = async (config, context) => {
  const federatedModules = await withModuleFederation({
    // your options here
  });

  return merge(federatedModules(config, context), {
    // overwrite values here
  });
};
```

Reference the [webpack documentation](https://webpack.js.org/configuration/) for details on the structure of the webpack
config object.

## Next.js Applications

Next.js supports webpack customization in the `next.config.js` file.

```js
const { withNx } = require('@nrwl/next/plugins/with-nx');

const nextConfig = {
  webpack: (
    config,
    { buildId, dev, isServer, defaultLoaders, nextRuntime, webpack }
  ) => {
    // Important: return the modified config
    return config;
  },
};

return withNx(nextConfig);
```

Read the [official documentation](https://nextjs.org/docs/api-reference/next.config.js/custom-webpack-config) for more details.